Ceramic modules, such as single chip packages and multi-chip modules (MCMs), are typically mounted in sockets for electrical testing. The sockets include conductive contacts which electrically connect to conductive pads located on the ceramic modules. The sockets can also be used for interconnecting the ceramic module to a printed circuit board. In either case, the input and output conductive pads of the ceramic module must be accurately mated with the corresponding conductive contacts of the socket.
FIG. 1 and FIG. 2 show a ceramic module 10 and a socket 11. The ceramic module 10 includes conductive pads 12 which must make registration contact with conductive contacts 13 of the socket 11. Typically, this is done by using the physical edges 14 of the ceramic module 10 as a method of aligning the conductive pads 12 with conductive contacts 13 (often referred to as "edge alignment"). For this method to properly work, the registration tolerance of the input and output conductive pads 12 of the ceramic module 10 with respect to the edges 14 of the ceramic module 10 must be small enough in relation to the pitch of the conductive pads 12 to provide proper mating between the conductive pads 12 and the conductive contacts 13.
The edge alignment described is simple and effective in most applications. However, with finer pitches between the conductive pads 12, are registration tolerance between the edges 14 of the ceramic module 10 and the conductive pads 12 is too large to provide acceptable alignment between the conductive pads 12 and the conductive contacts 13.
Two approaches have been used to improve the registration tolerance of a ceramic module. The first approach includes grinding the edges of the ceramic module. The edge are ground after a co-firing of the module to achieve better registration between the edges and the pattern of the conductive pads. The second approach includes dividing the co-firing of the module into two stages. The first stage includes co-firing all layers of the ceramic module except the conductive pad layer. The second stage includes co-firing the conductive pads onto the previously fired layers.
Both of the described approaches add extra processing steps. Consequently, both approaches are very expensive.
It is desirable to have an apparatus and method of aligning the conductive pads of a ceramic module with conductive contacts of a socket which does not require expensive process steps to improve the registration of the edges of the ceramic module with respect to the location of the conductive pads. Furthermore, the apparatus and method would not require any other expensive processing steps.